1. Field of the Disclosure
The disclosure relates to a Roots pump.
2. Discussion of the Background Art
Roots pumps typically comprise two-toothed rotary pumps arranged in a pump chamber. The two rotary pistons are driven in opposite directions so that the individual chambers formed draw gas through a main inlet and expel the gas through a main outlet. Here, the main inlet and the main outlet both extend in a radial direction and are arranged opposite each other. Further, multi-toothed rotary pistons are known, in particular such pistons with three or four teeth. In this case, too, the gas is pumped substantially radially from a radially arranged main inlet to a radially arranged main outlet.
Further, for producing low pressures, multi-stage Roots pumps are known. Such Roots pumps comprise one pair of rotary pistons per stage. Here, the gas to be pumped is conveyed from one outlet of a pump stage to the inlet of an adjacent pump stage. This is effected through connection channels. As described, for instance, in U.S. 2010/0158728, these connection channels may be arranged in the housing of the Roots pump, wherein the connection channels surround or are arranged radially outside the pump chambers in which the rotary pumps are arranged. This is necessary in order to convey gas from an outlet of a pump stage situated, for instance, in the lower part of the Roots pump to a pump inlet of the adjacent pump stage, which inlet is situated, for instance, in the opposite, upper part of a Roots pump. Such Roots pumps are disadvantageous in that the design of the channels in the housing is technically complex. Further, the housing volume must be large in order to accommodate the connection channels. This does not only result in large outer dimensions of the Roots pump, but in particular entails high costs. Besides the complex manufacturing process, the high costs are due also to the large quantity of metal used.
It is an object of the disclosure to provide a Roots pump of technically simple construction, wherein, further, the necessary structural space and the costs are preferably reduced.